Heretofore, a honeycomb structure made of cordierite onto which a catalyst is loaded has been used in treatment of a harmful substance in an exhaust gas discharged from a car engine. Moreover, it is also known that a honeycomb structure formed by a sintered silicon carbide body has been used in purification of the exhaust gas (see, for example, Patent Document 1).
When the exhaust gas is treated with the catalyst loaded onto the honeycomb structure, a temperature of the catalyst needs to be raised to a predetermined temperature. However, the catalyst temperature is low at the start of the engine. This has caused the problem that the exhaust gas is not sufficiently purified.
Accordingly, a method in which a heater made of a metal is disposed on an upstream side of a honeycomb structure onto which a catalyst is loaded to raise a temperature of an exhaust gas has been investigated (for example, see Patent Document 2). Additionally, a method in which the catalyst is loaded on a heater made of a metal for use has been investigated (for example, see Patent Document 3).